Read head sensor with balanced shield design

ABSTRACT

The present disclosure generally relates to a read head of a data storage device. The read head includes a read sensor sandwiched between two shields. The shields can have different materials as well as a different number of layers. Furthermore the shields can be fabricated by different processes and have different heights and thicknesses. The ratio of the thickness to the height for the shields are substantially identical to ensure that the saturation field are substantially identical and balanced.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

Embodiments of the present disclosure generally relate to a read head ofa data storage device.

Description of the Related Art

The heart of the functioning and capability of a computer is the storingand writing of data to a data storage device, such as a hard disk drive(HDD). The volume of data processed by a computer is increasing rapidly.There is a need for higher recording density of a magnetic recordingmedium to increase the function and the capability of a computer.

In order to achieve higher recording densities, such as recordingdensities exceeding 2 Tbit/in² for a magnetic recording medium, thewidth and pitch of write tracks are narrowed, and thus the correspondingmagnetically recorded bits encoded in each write track are narrowed.Attempts to achieve increasing requirements of advanced narrow gapreader sensors of read heads to achieve reading of higher recordingdensities have been proposed utilizing magnetoresistive sensors withfree layers comprised of high saturation magnetization materials.

Typical read heads include a read sensor sandwiched between two shields.Obtaining a balanced saturation field of shields for a read head can bechallenging as the shields are not always identical which can create anunbalanced out of plane magnetic field.

Therefore, there is a need in the art for an improved magnetic readhead.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to a read head of a datastorage device. The read head includes a read sensor sandwiched betweentwo shields. The shields can have different materials as well as adifferent number of layers. Furthermore the shields can be fabricated bydifferent processes and have different heights and thicknesses. Theratio of the thickness to the height for the shields are substantiallyidentical to ensure that the saturation field of individual shields aresubstantially identical and balanced.

In one embodiment, a magnetic read head comprises: a first shield, thefirst shield having a first thickness and a first height; a sensordisposed on the first shield; and a second shield disposed on thesensor, wherein the second shield has a second thickness and a secondheight, wherein the first thickness and the second thickness aredifferent, and wherein a ratio of the first thickness to the firstheight is substantially identical to a ratio of the second thickness tothe second height.

In another embodiment, a magnetic read head comprises: a first shield,wherein the first shield comprises a single layer; a sensor disposed onthe first shield; and a second shield disposed on the sensor, whereinthe second shield comprises a plurality of layers, and wherein the firstshield and the second shield have substantially identical magneticsaturation fields.

In another embodiment, a magnetic read head comprises: a first shieldcomprising a single, first layer, wherein the first layer has a firstthickness and a first height; a sensor disposed on the first shield,wherein the sensor is a dual free layer sensor; and a second shielddisposed on the sensor, wherein the second shield comprises a pluralityof layers, wherein the plurality of layers has a second thickness and asecond height, and wherein the first thickness is different from thesecond thickness, and wherein a ratio of the first thickness to thefirst height is substantially identical to a ratio of the secondthickness to the second height.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 is a schematic illustration of certain embodiments of a magneticmedia drive including a magnetic read head.

FIG. 2 is a schematic illustration of certain embodiments of a crosssectional side view of a head assembly facing a magnetic storage medium.

FIGS. 3A and 3B are schematic illustrations of read heads having shieldswith different heights and thicknesses according to embodimentsdiscussed herein.

FIGS. 3C-3E are schematic illustrations of read heads having shieldswith different layers according to embodiments discussed herein.

FIG. 3F is a schematic illustration of a read head having a dual freelayer sensor according to one embodiment.

FIG. 3G is a schematic illustration of a read head having a single freelayer sensor according to one embodiment.

FIG. 4 is a graph illustrating a linearity improvement according toembodiments discussed herein.

FIG. 5 is a graph illustrating disturbance to a rear hard bias (RHB)structure and transfer curve flip according to embodiments discussedherein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

In the following, reference is made to embodiments of the disclosure.However, it should be understood that the disclosure is not limited tospecific described embodiments. Instead, any combination of thefollowing features and elements, whether related to differentembodiments or not, is contemplated to implement and practice thedisclosure. Furthermore, although embodiments of the disclosure mayachieve advantages over other possible solutions and/or over the priorart, whether or not a particular advantage is achieved by a givenembodiment is not limiting of the disclosure. Thus, the followingaspects, features, embodiments and advantages are merely illustrativeand are not considered elements or limitations of the appended claimsexcept where explicitly recited in a claim(s). Likewise, reference to“the disclosure” shall not be construed as a generalization of anyinventive subject matter disclosed herein and shall not be considered tobe an element or limitation of the appended claims except whereexplicitly recited in a claim(s). Usage in the Summary of the Disclosureor in the Detailed Description of the term “comprising” shall meancomprising, consisting essentially, and/or consisting of.

The present disclosure generally relates to a read head of a datastorage device. The read head includes a read sensor sandwiched betweentwo shields. The shields can have different materials as well as adifferent number of layers. Furthermore the shields can be fabricated bydifferent processes and have different heights and thicknesses. Theratio of the thickness to the height for the shields are substantiallyidentical to ensure that the saturation field are substantiallyidentical and balanced.

FIG. 1 is a schematic illustration of certain embodiments of a magneticmedia drive 100 including a magnetic write head and a magnetic readhead. The magnetic media drive 100 may be a single drive/device orcomprise multiple drives/devices. The magnetic media drive 100 includesa magnetic recording medium, such as one or more rotatable magnetic disk112 supported on a spindle 114 and rotated by a drive motor 118. For theease of illustration, a single disk drive is shown according to oneembodiment. The magnetic recording on each magnetic disk 112 is in theform of any suitable patterns of data tracks, such as annular patternsof concentric data tracks (not shown) on the magnetic disk 112.

At least one slider 113 is positioned near the magnetic disk 112. Eachslider 113 supports a head assembly 121 including one or more read/writeheads, such as a write head and such as a read head comprising a TMRdevice. As the magnetic disk 112 rotates, the slider 113 moves radiallyin and out over the disk surface 122 so that the head assembly 121 mayaccess different tracks of the magnetic disk 112 where desired data arewritten or read. Each slider 113 is attached to an actuator arm 119 byway of a suspension 115. The suspension 115 provides a slight springforce which biases the slider 113 toward the disk surface 122. Eachactuator arm 119 is attached to an actuator 127. The actuator 127 asshown in FIG. 1 may be a voice coil motor (VCM). The VCM includes a coilmovable within a fixed magnetic field, the direction and speed of thecoil movements being controlled by the motor current signals supplied bycontrol unit 129.

During operation of the magnetic media drive 100, the rotation of themagnetic disk 112 generates an air or gas bearing between the slider 113and the disk surface 122 which exerts an upward force or lift on theslider 113. The air or gas bearing thus counter-balances the slightspring force of suspension 115 and supports slider 113 off and slightlyabove the disk surface 122 by a small, substantially constant spacingduring normal operation.

The various components of the magnetic media drive 100 are controlled inoperation by control signals generated by control unit 129, such asaccess control signals and internal clock signals. Typically, thecontrol unit 129 comprises logic control circuits, storage means and amicroprocessor. The control unit 129 generates control signals tocontrol various system operations such as drive motor control signals online 123 and head position and seek control signals on line 128. Thecontrol signals on line 128 provide the desired current profiles tooptimally move and position slider 113 to the desired data track on disk112. Write and read signals are communicated to and from the headassembly 121 by way of recording channel 125. Certain embodiments of amagnetic media drive of FIG. 1 may further include a plurality of media,or disks, a plurality of actuators, and/or a plurality number ofsliders.

FIG. 2 is a schematic illustration of certain embodiments of a crosssectional side view of a head assembly 200 facing the magnetic disk 112or other magnetic storage medium. The head assembly 200 may correspondto the head assembly 121 described in FIG. 1. The head assembly 200includes a media facing surface (MFS) 212 facing the magnetic disk 112.As shown in FIG. 2, the magnetic disk 112 relatively moves in thedirection indicated by the arrow 232 and the head assembly 200relatively moves in the direction indicated by the arrow 233.

The head assembly 200 includes a magnetic read head 211. The magneticread head 211 include a sensing element 204 disposed between shields S1and S2. The sensing element 204 and the shields S1 and S2 having a MFS212 facing the magnetic disk 112. The sensing element 204 is a TMRdevice sensing the magnetic fields of the recorded bits, such asperpendicular recorded bits or longitudinal recorded bits, in themagnetic disk 112 by a TMR effect. In certain embodiments, the spacingbetween shields S1 and S2 is about 17 nm or less.

The head assembly 200 may optionally include a write head 210. The writehead 210 includes a main pole 220, a leading shield 206, and a trailingshield (TS) 240. The main pole 220 comprises a magnetic material andserves as a main electrode. Each of the main pole 220, the leadingshield 206, and the trailing shield (TS) 240 has a front portion at theMFS. The write head 210 includes a coil 218 around the main pole 220that excites the main pole 220 producing a writing magnetic field foraffecting a magnetic recording medium of the rotatable magnetic disk112. The coil 218 may be a helical structure or one or more sets ofpancake structures. The TS 240 comprises a magnetic material, serving asa return pole for the main pole 220. The leading shield 206 may provideelectromagnetic shielding and is separated from the main pole 220 by aleading gap 254.

FIGS. 3A and 3B are schematic illustrations of read heads having shieldswith different heights and thicknesses according to embodimentsdiscussed herein. FIGS. 3C-3E are schematic illustrations of read headshaving shields with different layers according to embodiments discussedherein. FIG. 3F is a schematic illustration of a read head having a dualfree layer sensor according to one embodiment. FIG. 3G is a schematicillustration of a read head having a single fee layer sensor accordingto one embodiment. The read heads of FIG. 3A-3G include a first shield(S1) 302, a sensor 304 disposed on the S1 302, and a second shield (S2)306 disposed on the sensor 304.

In FIGS. 3A and 3B, the S1 302 has a first thickness and a first heightand the S2 306 has a second thickness and a second height. The firstthickness 342 of the S1 302 and the second thickness 344 of the S2 306each has a thickness of about 0.1 microns to about 2 microns.Furthermore, the first height 346 of the S1 302 and the second height348 of the S2 306 each has a height of about 10 microns to about 20microns. The previous ranges of values listed for the thickness and theheight of the S1 and the S2 is not intended to be limiting, but toprovide an example of possible embodiments. In one embodiment, the firstthickness is not equal to the second thickness, and the first height isnot equal to the second height.

If the first height 346 of S1 302 is about 20 microns, the second height348 of S2 306 is about 10 microns, the first thickness 342 of S1 302 isabout 2 microns, and the second thickness 344 of S2 306 is about 1microns, then the ratio of the first thickness 342 of S1 302 to thefirst height 346 of S1 302 is about 2:20 or about 0.1 and the ratio ofthe second thickness 344 of S2 306 to the second height 348 of S2 306 isabout 1:10 or about 0.1. If the first height 346 of S1 302 is about 10microns, the second height 348 of S2 306 is about 20 microns, the firstthickness 342 of S1 302 is about 1 microns, and the second thickness 344of S2 306 is about 2 microns, then the ratio of the thickness of S1 302to the height of S1 302 is about 1:10 or about 0.1 and the ratio of thethickness of S2 306 to the height of S2 306 is about 2:20 or about 0.1.

The saturation field of each individual shield, S1 302 and S2 306, isproportional to the product of Ms (i.e., magnetic moment) of therespective shield times the ratio of the respective shield thickness tothe respective shield height. Though the S1 302 and the S2 306 may eachinclude different compositions of the materials previously mentioned,the saturation field of the S1 and the S2 are substantially identicaldue to the relationship between the product of the first shield Ms timesthe ratio of the first thickness 342 to the first height 346 of the S1302 and product of the second shield Ms times the ratio of the secondthickness 344 to the second height 348 of the S2 306. Likewise, the outof plane magnetic fields (seen by reader) from the S1 302 and the S2 306are substantially cancelled due to the relationship between the productof the first shield Ms times the ratio of the first thickness 342 to thefirst height 346 of the S1 302 and the product of the second shield Mstimes the ratio of the second thickness 344 to the second height 348 ofthe S2 306.

The ratio of the first thickness 342 to the first height 346 of the S1302 is equal to or substantially identical to the ratio of the secondthickness 344 to the second height 348 of the S2 306, such that theequation, Ms₁T₁/H₁=Ms2T₂/H₂ is satisfied. For example, for the sameshield material, which implies the same Ms, if the first thickness 342is equal to about 1 micron and the first height 346 is equal to about 10microns, the ratio of the first thickness 342 to the first height 346 isabout 1:10 or about 0.1. Therefore, in order for the ratio of the secondthickness 344 to the second height 348 to be equal to or substantiallyidentical to the ratio of the first thickness 342 to the first height346, the second thickness 344 and the second height 348 should satisfythe following equations: T_(2=0.1)*H₂ or H₂=T₂/0.1, where T₂ refers tothe second thickness 344 and H₂ refers to the second height 348.

The S1 302 and the S2 306 include materials selected from the group thatincludes amorphous magnetic alloys, such as nickel (Ni), iron (Fe),cobalt (Co), chromium (Cr), zirconium (Zr), niobium (Nb), hafnium (Hf),and combinations thereof. In one embodiment, the Ms of the shieldingmaterial is the same in S1 302 and S2 306. In another embodiment, the Msof the shielding material has over 100% difference in magnitude asbetween that of S1 and S2. The S1 302 and the S2 306 may each be formedthrough a first method or through different methods, such as a firstmethod to form S1 302 and a second method to form S2 306. Methods toform the S1 302 and the S2 306 include chemical vapor deposition (CVD),atomic layer deposition (ALD), physical vapor deposition (PVD),electroplating, and the other methods appropriate to forming a shield.

FIG. 3C is a schematic illustration of a read head including a S1 302, asensor 304 disposed on the S1 302, and a plurality of S2 layers 306a-306 n, with n representing 4 or more, where a first S2 layer 306 a isdisposed on the sensor 304 and each subsequent S2 layer 306 b-306 n isdisposed on the previous S2 layer 306 b-306 n. As shown in FIG. 3C, thesecond S2 layer 306 b is disposed on the first S2 layer 306 a, the thirdS2 layer 306 c is disposed on the second S2 layer 306 b, and so-forth.The S1 302 may be formed by a first method that includes a firstmaterial. Furthermore, each of the one or more S2 layers 306 a-306 n maybe formed by a second method that is different from the first method ofthe S1 302 that includes a second material that is different from thefirst material. The materials and methods of forming each shield of aread head include the previously listed methods and materials applicableto the shield of a read head. Furthermore, each layer of the one or moreS2 layers 306 a-306 n may comprise identical or different materials andbe formed by identical or different methods.

FIG. 3D is a schematic illustration of a read head including a pluralityof S1 302 a-302 n, with n representing 4 or more, a sensor 304 disposedon the plurality of S1 302 a-302 n, and a S2 layer 306, where the last51 layer 302 n is disposed adjacent to and in contact with the sensor304. As shown in FIG. 3D, the second 51 layer 302 b is disposed on thefirst 51 layer 302 a, the third 51 layer 302 c is disposed on the secondS1 layer 302 b, and so forth. The S2 306 may be formed by a first methodthat includes a first material. Furthermore, each of the one or more 51layers 302 a-302 n may be formed by a second method that is differentfrom the first method of the S2 306 that includes a second material thatis different from the first material. The materials and methods offorming each shield of a read head include the previously listed methodsand materials applicable to the shield of a read head. Furthermore, eachlayer of the one or more S1 layers 302 a-302 n may comprise identical ordifferent materials and be formed by identical or different methods.

FIG. 3E is a schematic illustration of a read head including a pluralityof S1 302 a-302 n, with n representing 4 or more, a sensor 304 disposedon the plurality of S1 302 a-302 n, and a plurality of S2 306 a-306 n(with n representing 4 or more) disposed on the sensor 304. As shown inFIG. 3E, the second S1 layer 302 b is disposed on the first S1 layer 302a, the third S1 layer 302 c is disposed on the second S1 layer 302 b,and so forth. Additionally as shown in FIG. 3E, a first S2 layer 306 ais disposed on the sensor 304 and each subsequent S2 layer 306 b-306 nis disposed on the previous S2 layer 306 b-306 n such that the second S2layer 306 b is disposed on the first S2 layer 306 a, the third S2 layer306 c is disposed on the second S2 layer 306 b, and so forth.

Each of the one or more S1 layers 302 a-302 n may be formed by a firstmethod that is different from the second method of forming the one ormore S2 layers 306 a-306 n. Furthermore, the materials for the one ormore S1 layers 302 a-302 n may comprise a first material that isdifferent from a second material that comprises the one or more S2layers 306 a-306 n. Additionally, the different layers of S1 302 a-302 nmay comprise different materials. Similarly, the different layers of S2306 a-306 n may comprise different materials. The materials and methodsof forming each shield of a read head include the previously listedmethods and materials applicable to the shield of a read head.Furthermore, each layer of the one or more S1 layers 302 a-302 n and theone or more S2 layers 306 a-306 n may comprise identical or differentmaterials and be formed by identical or different methods.

FIG. 3F is a schematic illustration of a read head, according to oneembodiment, including a first shield (S1) 302, a dual free layer (DFL)sensor 304, a second shield (S2) 306, an insulation 320, a rear hardbias (RHB) 318, and a nonmagnetic layer 322. The sensor 304 includes aseed layer 308, a first free layer (FL) 310, a barrier layer (such asMgO) 312, a second FL 314, and a cap layer 316. Because the sensor 304includes two FLs 310, 314, the sensor 304 may be considered a dual freelayer (DFL) sensor. The sensor 304 may be a magnetic tunnel junction(MTJ) stack and may be formed using PVD sputtering, IBD, and otherwell-known deposition methods. The seed layer 308 includes a materialselected from the group that includes tantalum (Ta), tungsten (W), Ru,Cr, Co, Ti, Hf, and combinations thereof. The cap layer 316 may be Ta,Ru, Cr, Ti, Hf or any other suitable cap material. The insulation 320may be MgO, aluminum oxide (AlOx), SiN or any other suitable insulationmaterial. Free layers may each include Ni, Fe, Co, boron, Hf orcombinations thereof. The rear hard bias (RHB) 318 may include cobaltplatinum (CoPt) or CoCrPt with high coercivity sitting on an appropriateseed layer to generate a magnetic field that acts on the sensor 304.Furthermore, a nonmagnetic layer 322 separates the RHB 318 from the S2306, such that the RHB 318 is not in contact with the S2 306.

FIG. 3G is a schematic illustration of a read head having a single freelayer sensor according to one embodiment. The read head includes a firstshield (S1) 302, a sensor 380, a second shield (S2) 306, and aninsulation 320. The sensor 380 includes a seed layer 382, a fixedmagnetic layer 384, a barrier layer 386, a free layer (FL) 388, and acap layer 390. The sensor 380 is a magnetic tunnel junction (MTJ) stackand may be formed using PVD sputtering, IBD, and other well-knowndeposition methods. The seed layer 382 includes a material selected fromthe group that includes tantalum (Ta), tungsten (W), Ru, Cr, Co, Ti, andcombinations thereof. The cap layer 390 may be Ta, Ru, Cr, Ti, Hf or anyother suitable cap material. The barrier layer 386 may be MgO, aluminumoxide (AlOx) or any other suitable insulation material. The free layer388 and the fixed layer 384 include Ni, Fe, Co, boron, Hf orcombinations thereof.

To this point, the examples have assumed that S1 and S2 have the sameMs, yet different heights and thicknesses such that the ratio ofMs1T₁/H₁=Ms2T₂/H₂. However, it is to be understood that S1 and S2 mayhave different materials (hence different Ms) as well as differentthicknesses and heights, yet still satisfy the equationMs₁T₁/H₁=Ms2T₂/H₂.

FIG. 4 is a graph illustrating a reader linearity improvement accordingto embodiments discussed herein. The applied field, H (Oe), is graphedon the x-axis and the net out-of-plane field from shield, seen by sensorHz (Oe), is graphed on the y-axis. The solid line is the base case whereboth S1 and S2 have the same Ms, where the ratio of the thickness to theheight of the first shield, such as S1 302, and ratio of the thicknessto the height of the second shield, such as S2 306, are notsubstantially identical. The dotted line case has the Ms of the firstshield times the ratio of the thickness to the height of the firstshield identical to the Ms of the second shield times the ratio of thethickness to the height of the second shield. Further, the first shieldheight is equal to the second shield height in the dotted line case.Because the ratio of the thickness to the height of each shield issubstantially identical and because the Ms are the same for bothshields, the out-of-plane fields are effectively canceled (e.g., closerto 0 on the y-axis), resulting in a more linearized and improved sensortransfer curve and a smaller asymmetrical standard deviation.

FIG. 5 is a graph illustrating disturbance to a rear hard bias (RHB)structure in the case where a DFL sensor is implemented and transfercurve flip according to embodiments discussed herein. The transversefield, H(Oe), is graphed on the x-axis and the out-of-plane field, Hz(Oe), is graphed on the y-axis. The solid line is the base case, wherethe ratio of the thickness to the height of the first shield, such as S1302, and ratio of the thickness to the height of the second shield, suchas S2 306, are not substantially identical. The dotted line case has theMs of the first shield times the ratio of the thickness to the height ofthe first shield substantially identical to the Ms of the second shieldtimes the ratio of the thickness to the height of the second shield.Moreover, the first shield height is equal to the second shield heightof the dotted line case. A typical DFL design usually includes a RHB,such as RHB 318 of FIG. 3F. The un-cancelled out-of-plane fieldsgenerated by the opposing shields (e.g., a first shield and a secondshield) may have a negative effect (e.g., a polarity flip), if they arecloser or larger than the coercivity of the RHB, and may: (1) disturbmagnetization of RHB, and (2) in an extreme case, flip the RHBdirection, resulting in polarity flip of sensor transfer curve.

Because the Ms of the shield times the ratio of the thickness to theheight of each shield is substantially identical, the out-of-planefields are effectively cancelled or minimized (e.g., closer to 0 on they-axis), resulting in little or no impact on RHB and no polarity flip ofthe sensor and improved sensor performance.

It is to be understood that the magnetic recording head discussed hereinis applicable to a data storage device such as a hard disk drive (HDD)as well as a tape drive such as a tape embedded drive (TED) or aninsertable tape media drive. An example TED is described in co-pendingU.S. patent application entitled “Tape Embedded Drive”, application Ser.No. 16/365,034, filed on Mar. 31, 2019 and assigned to the same assigneeof the instant application, which is incorporated by reference herein.As such, any reference in the detailed description to a HDD or tapedrive is merely for exemplification purposes and is not intended tolimit the disclosure unless explicitly claimed. Furthermore, referenceto or claims directed to magnetic recording devices are intended toinclude both HDD and tape drive unless HDD or tape drive devices areexplicitly claimed.

In one embodiment, a magnetic read head comprises: a first shield, thefirst shield having a first thickness and a first height; a sensordisposed on the first shield; and a second shield disposed on thesensor, wherein the second shield has a second thickness and a secondheight, wherein the first thickness and the second thickness aredifferent, and wherein a ratio of the first thickness to the firstheight is substantially identical to a ratio of the second thickness tothe second height. Both the first thickness and the second thickness arebetween about 0.5 microns and about 2 microns. Both the first height andthe second height are between about 10 microns and about 20 microns. Thesensor comprises a dual free layer sensor. The first shield and thesecond shield have substantially identical Ms. The first shield and thesecond shield have different values for Ms, and wherein Ms for the firstshield times the first thickness divided by the first height equals Msfor the second shield times the second thickness divided by the secondheight. A magnetic media drive comprising the magnetic read head is alsodisclosed.

In another embodiment, a magnetic read head comprises: a first shield,wherein the first shield comprises one or more first shield layers; asensor disposed on the first shield; and a second shield disposed on thefirst shield, wherein the second shield comprises one or more secondshield layers, wherein one or more of the first shield and the secondshield comprises a plurality of layers, and wherein the first shield andthe second shield have substantially identical magnetic saturationfields. The sensor is a single free layer sensor. At least one layer ofthe plurality of layers of the second shield is formed by a method thatis different from a method used to form the first shield. The firstshield comprises a first material, wherein the second shield comprises asecond material that is different from the first material. The firstshield has a first thickness and first height, wherein the second shieldhas a second thickness and a second height, and wherein the first heightis different from the second height. A ratio of the first thickness tothe first height is substantially identical to a ratio of the secondthickness to the second height. The magnetic read head further comprisesa magnetic hard bias structure disposed between the first shield and thesecond shield. A magnetic media drive comprising the magnetic read headis also disclosed.

In another embodiment, a magnetic read head comprises: a first shieldcomprising a single, first layer, wherein the first layer has a firstthickness and a first height; a sensor disposed on the first shield,wherein the sensor is a dual free layer sensor; and a second shielddisposed on the sensor, wherein the second shield comprises a pluralityof layers, wherein the plurality of layers has a second thickness and asecond height, and wherein the first thickness is different from thesecond thickness, and wherein a ratio of the first thickness to thefirst height is substantially identical to a ratio of the secondthickness to the second height. Out of plane magnetic fields from thefirst shield and the second shield are substantially cancelled. Amagnetic saturation field of the first shield is substantially identicalto a magnetic saturation field of the second shield. The sensor is asingle free layer sensor. When the sensor is a dual free layer sensor,the magnetic read head further comprises a magnetic hard bias structuredisposed behind the sensor and between the first shield and the secondshield. A magnetic media drive comprising the magnetic read head is alsodisclosed.

By using shields having different materials, different number of layers,fabricated by different processes, and or having different heights andthicknesses, keeping the ratio of the thickness to the height for theshields to be substantially identical ensures that the saturation fieldare substantially identical and balanced.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A magnetic read head, comprising: a first shield,the first shield having a first thickness and a first height; a sensordisposed on the first shield; and a second shield disposed on thesensor, wherein the second shield has a second thickness and a secondheight, wherein the first thickness and the second thickness aredifferent, and wherein a ratio of the first thickness to the firstheight is substantially identical to a ratio of the second thickness tothe second height.
 2. The magnetic read head of claim 1, wherein boththe first thickness and the second thickness are between about 0.5microns and about 2 microns.
 3. The magnetic read head of claim 1,wherein both the first height and the second height are between about 10microns and about 20 microns.
 4. The magnetic read head of claim 1,wherein the sensor comprises a dual free layer sensor.
 5. The magneticread head of claim 1, wherein the first shield and the second shieldhave substantially equal magnetic moments (Ms).
 6. The magnetic readhead of claim 1, wherein the first shield and the second shield havedifferent values for Ms, and wherein Ms for the first shield times thefirst thickness divided by the first height equals Ms for the secondshield times the second thickness divided by the second height.
 7. Amagnetic media drive comprising the magnetic read head of claim
 1. 8. Amagnetic read head, comprising: a first shield comprising a single,first layer, wherein the first layer has a first thickness and a firstheight; a sensor disposed on the first shield, wherein the sensor is adual free layer sensor; and a second shield disposed on the sensor,wherein the second shield comprises a plurality of layers, wherein theplurality of layers has a second thickness and a second height, andwherein the first thickness is different from the second thickness, andwherein a ratio of the first thickness to the first height issubstantially identical to a ratio of the second thickness to the secondheight.
 9. The magnetic read head of claim 8, wherein out of planemagnetic fields from the first shield and the second shield aresubstantially cancelled.
 10. The magnetic read head of claim 8, whereina magnetic saturation field of the first shield is substantiallyidentical to a magnetic saturation field of the second shield.
 11. Themagnetic read head of claim 8, wherein the sensor comprises a rear hardbias structure.
 12. A magnetic media drive comprising the magnetic readhead of claim 8.